Effects of D 1 receptor agonist SKF 38393 on male rat sexual behavior and postcopulatory departure in the goal compartment–runway paradigm

Abstract

Male rats were tested in an apparatus in which the goal compartment of the runway was connected with the start compartment by a one-way door. In this apparatus, the male spontaneously left the goal compartment containing the estrous female after a mount bout (the cluster of one or more copulatory events) and a new run started. This effect (the postcopulatory departure) seems to be due to the competition between the incentive value of the stimulus female and the runway. The dopamine D 1 receptor agonist SKF 38393 at the doses of 1–5 mg/kg sc significantly prolonged the time spent by the male in the goal compartment, while both run latency and run duration remained unaffected. Further analysis showed that the prolongation of the time in goal compartment results from increased duration of copulatory behavior accompanied by increased number of copulatory events. Although SKF 38393 did not influence the latency of postcopulatory departures, incomplete departures occurred in five out of eight males. In the free access to female conditions, the SKF 38393 did not influence copulatory performance, except for a reduction in the number of intromissions at the dose of 1 mg/kg sc. On the other hand, a significant reduction of postejaculatory ultrasonic vocalization was observed.